I'm trying to get a feel for what degrees of cold exist, and what effect
they have, and what countermeasures are necessary and appropriate. (For
definiteness, assume the context is either a tide-locked planet where
the atmosphere is dense enough to be breathable but not so dense that
the temperature on the night side doesn't drop very low indeed; or
someplace like Titan that's just plain chilly all round, but still has
normal atmospheric pressure. I have outline ideas regarding both of
those for a possible future setting.)
Here's my understanding so far. (All temperatures given in Celsius.)
The lowest temperature I've ever personally been exposed to is something
like -5, maybe -10. This range is still comfortable provided you're
dressed reasonably warmly; there aren't any qualitatively new effects,
at least when you're walking around by day. (I didn't have to try
sleeping rough in it.)
Frostbite becomes a significant concern at what, somewhere past -20?
When you're getting towards -40, another qualitative difference seems to
start setting in; I've read accounts from Napoleon's retreat from Moscow
that described what happened when it hit -37.5; people weren't just
getting frostbite or dying overnight anymore, they were dropping dead
mid-stride with blood pouring from ears and eyes. (What's the mechanism
for that?)
Of course, the people in question didn't have adequate cold-weather
clothing; people who do possess such, seem to be able to function
adequately at -40 without safety becoming an unreasonably difficult
problem.
At what point does it start becoming a) dangerous and b) impossible to
function no matter how warmly you're dressed?
I believe the coldest it ever gets in inhabited regions is something
like -60, and the coldest ever recorded on Earth is -89?
But there's plenty further to go than that. The temperature on Titan is
about -180, just above the boiling point of oxygen. The pressure on
Titan is comfortable, so in theory you could go around in a parka and an
oxygen mask, but I'm sure the cold would kill you quickly.
At what point do you start needing something like a full environment
suit? Are there any more qualitative differences after you reach that
point?
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